This is no problem at all on the easy difficulty. There are 12 chapters in total, and this will pop up just as you enter the shuttle at the end of the last chapter. I'd recommend you play this difficulty first (or medium) to get a feel for the game and to familiarise yourself with the levels, especially if you want to attempt Epic Tier 3 Engineer. You'll have to do more than one playthrough anyway in order to get Maxed Out, and probably some of the weapon-related achievements.
Note: As crazy as it sounds, One Gun should probably be attempted at the same time as Epic Tier 3 Engineer. Reason being, the more weapons you have the more ammo you have to buy for them. With only one weapon to cater for (the plasma cutter is a solid all-round weapon anyway) it gives you more money for health packs, which you'll definitely be needing.